Subsea sampling system and method

ABSTRACT

A system and method are provided for collecting fluid samples from a fluid flowline located subsea. The system includes a multiphase sampling apparatus attachable to the flowline, and a vehicle sampling apparatus that is connectable to the multiphase sampling apparatus to allow the transfer of the collected fluid sample thereto. The vehicle sampling apparatus is preferably a subsea remotely operated vehicle (ROV) locatable proximate the fluid flowline and having a fluid sample collector and a fluid pump for transferring the collected fluid sample from the multiphase sampling apparatus to the fluid sample collector. The vehicle sampling apparatus includes a fluid analysis sensor capable of extracting information about the collected fluid sample at a subsea location. Optionally, the vehicle sampling apparatus can transport the collected fluid sample to a location remote from the fluid flowline for analysis.

CROSS REFERENCE TO RELATED APPLICATIONS

The present disclosure is based on and claims the benefit of priorityfrom U.S. Provisional Patent Application Ser. No. 61/160,446 of Brown etal, entitled “SUBSEA SAMPLING SYSTEM AND METHOD,” filed on Mar. 16,2009; U.S. Provisional Patent Application Ser. No. 61/166,998 of Brownet al, entitled “SUBSEA SAMPLING SYSTEM AND METHOD,” filed on Apr. 6,2009; U.S. Provisional Patent Application Ser. No. 61/232,487 of Brownet al., entitled “ISOTHERMAL SUBSEA SAMPLING SYSTEM AND METHOD,” filedon Aug. 10, 2009; and U.S. Provisional Patent Application Ser. No.61/285,323 of Theron et al, entitled “SUBSEA SAMPLING SYSTEM ANDMETHOD,” filed on Dec. 10, 2009; the entire contents of the disclosuresof which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates generally to sampling fluids in the oiland gas industry. More particularly, the present disclosure relates toan apparatus, system and method for sampling fluids subsea.

DISCUSSION OF THE BACKGROUND

In the oil and gas industry, fluid samples are collected for analysis inmany well applications. For example, in a subsea environment tubing isused to convey well fluid to a desired location. Measurements andsamples of the fluid moving through the tubing can provide usefulinformation for improved operation of the well.

Fluid samples, for example, may be collected for reservoircharacterization or to deduce reservoir fluid properties. The analysisgenerally is done at a land-based or field-deployedpressure/volume/temperature (PVT) laboratory. The information derived isused for periodic reservoir characterization over the life of a well tofacilitate the evaluation of reserves, and for production planning andoptimization.

Fluid samples are also collected to enable deposition studies, forexample, samples may be collected to carry out asphaltene depositionstudies. In subsea applications, problematic deposition of suchmaterials can occur as a result of the temperature and pressuregradients between a subsea wellhead and the surface.

In many of these same well applications, PVT data and hydrogen sulphide(H₂S) level data are used to facilitate optimization of a well fluidproduction. The PVT data, for example, can be used to correct volumetriccorrelations applied to flow meters, pipelines and other downstreamassets. However, the detection of the various well parameters and thetaking of samples for further analysis can be difficult and/orinefficient, particularly in certain environments, such as subseaenvironments.

Subsea sampling can be applied to single-phase or multiphase fluids.When the fluid is multiphase, the phases can be collected separately andanalyzed independently. This information can be used to reduce theuncertainty of the results obtained by using multiphase flow meters.

Various apparatus, methods and systems for sampling and analyzing wellfluids have been identified previously, including those used subsea.U.S. Pat. No. 6,435,279 discloses a method and apparatus for samplingfluids from an undersea wellbore utilizing a self-propelled underwatervehicle, and a collection and storage device.

International Patent Application PCT/EP2008/050445, published as WO2008/087156, discloses a system and method for analysis of fluidsamples. An article entitled “Improved Production Sampling Using theFramo Multiphase Flow Meter,” by Framo Engineering AS (October 1999)discusses a multiphase flow meter used in fluid sampling, includingsubsea with the aid of remotely operated vehicles (ROV).

Other technologies such as Schlumberger's MDT sampling and analysistechnologies have also been used for subsea sampling and analysis offluids in the oil and gas industry. A further well-known system used bySchlumberger for sampling fluids in the oil and gas industry is thePhaseSampler system and method.

SUMMARY OF THE INVENTION

In view of the foregoing disadvantages, problems, and insufficienciesinherent in the known types of methods, systems and apparatus present inthe prior art, exemplary implementations of the present disclosure aredirected to novel methods and systems for sampling fluids subsea.

According to an aspect of the present disclosure, a system forcollecting fluid samples from a fluid flowline is provided, the systemincluding a multiphase sampling apparatus and a vehicle samplingapparatus. The multiphase sampling apparatus is attachable to theflowline so as to collect a multiphase fluid sample from the flowline.The vehicle sampling apparatus is locatable proximate the fluidflowline, and is connectable to the multiphase sampling apparatus toallow transfer of the collected fluid sample thereto. The vehiclesampling apparatus includes a fluid sample collector, and a fluid pumpthat transfers the fluid sample from the multiphase sampling apparatusto the fluid sample collector.

The vehicle sampling apparatus may further include at least one fluidanalysis sensor capable of analyzing the collected fluid sample.Optionally, the vehicle sampling apparatus is capable of transportingthe collected fluid sample to a location remote from the fluid flowlinefor analysis.

The multiphase sampling apparatus may include a sampling probe that isinsertable into the fluid flow of the flowline and able to collect afluid sample, and the vehicle sampling apparatus may include a fluidconnector which allows the fluid sample collected by the multiphasesampling apparatus to be transferred to the vehicle sampling apparatus.

The system is preferably locatable subsea. In such an exemplaryembodiment of the present disclosure, the vehicle sampling apparatus ispreferably a subsea remotely operated vehicle (ROV) having theaforementioned fluid analysis sensor capable of analyzing the collectedfluid sample. In such an embodiment, the fluid analysis of the collectedsample may be performed either subsea or at surface. The fluid analysissensor may include sensors for measuring the nuclear attenuation of agamma ray source one phase at a time at line conditions.

The system may further include a plurality of fluid pumps which may beused for returning the fluid sample back into the fluid flowline,pressure testing the ROV connection, tuning a flow conditioner,maintaining line conditions within the fluid sample collector,unblocking or cleaning the sampling probe, the fluid connector orflowline, and/or deploying the sampling probe. Furthermore, the ROV mayinclude a full bore pipeline bypass for simplifying the intervention ofthe sampling probe.

Preferably the sampling probe may be inserted into the fluid flow of theflowline by means of an extension mechanism when a sample is to becollected. Further, the sampling probe may be retractable from the fluidflow of the flowline by means of the extension mechanism when thesampling probe is not to be used for taking a sample. The sampling probemay include at least one fluid analysis sensor.

In one aspect of the present disclosure, the multiphase samplingapparatus is permanently attached to the fluid flowline. In anotheraspect of the present disclosure, the multiphase sampling apparatus islocatable proximate the fluid flowline. In a further aspect of thepresent disclosure, the multiphase sampling apparatus is locatable onthe vehicle sampling apparatus.

Further in accordance with an aspect of the present disclosure, there isprovided a fluid enrichment mechanism for enriching the sample fluid.The enrichment mechanism of the collected fluid sample may furtherinclude a separation means for separating the phases of the multiphasefluid sample. The enrichment mechanism may further include means forseparately storing the phases of the fluid sample which are of interestand the enrichment mechanism may be capable of returning the unwantedphases of the fluid sample to the flowline.

According to another aspect of the present disclosure, a system forcollecting fluid samples from a subsea fluid flowline is provided, thesystem including a multiphase sampling apparatus attachable to a subseafluid flowline so as to be in communication with the fluid flow in theflowline, the multiphase sampling apparatus including a flow conditionerand sampling connector that may selectively communicate with the fluidflow for selective collection of a suitable fluid sample; and a vehiclesampling apparatus adapted for connection to the multiphase samplingapparatus, the vehicle sampling apparatus including a fluid connectorcapable of transferring the fluid sample between the multiphase samplingapparatus and the vehicle sampling apparatus; a fluid sample collectoradapted to contain the fluid sample for a selected period of time; afluid pump in communication with the fluid connector, and at least onefluid analysis sensor operable from a location remote from themultiphase sampling apparatus.

The fluid analysis sensor of the vehicle sampling apparatus may includea gamma ray attenuation sensor that may measure the nuclear attenuationof a gamma ray source one phase at a time, e.g. the measurement may bedone at line conditions in the vehicle sampling apparatus with gas onlyand then with liquid only.

The system may further include a plurality of fluid pumps for returningthe fluid sample back into the fluid flowline, pressure testing the ROVconnection, tuning the flow conditioner, maintaining line conditionswithin the fluid sample collector, unblocking or cleaning the samplingprobe, the fluid connector or flowline, and/or deploying the samplingprobe.

In another aspect of the present disclosure, the vehicle samplingapparatus may provide full bore pipeline bypass for intervention of themultiphase sampling apparatus.

Another aspect of the present disclosure provides a method forcollecting and analyzing fluid samples from a fluid flowline, the methodincluding the steps of: attaching a multiphase sampling apparatus to afluid flowline; collecting a fluid sample; attaching a vehicle samplingapparatus to the multiphase sampling apparatus; and transferring thefluid sample from the multiphase sampling apparatus to a fluid samplecollector of the vehicle sampling apparatus by means of a fluid pumpincluded in the vehicle sampling apparatus.

The method may further include the step of obtaining fluid informationrelating to the fluid sample from at least one fluid sensor locatable onthe vehicle sampling apparatus; and relaying the fluid information to aremote position.

The method may also further include the steps of inserting a samplingconnection of the multiphase sampling apparatus into the fluid flowlineand collecting a multiphase fluid sample, and connecting fluid conduitsbetween the multiphase sampling apparatus and the vehicle samplingapparatus prior to transferring the collected sample to the vehiclesampling apparatus.

The step of relaying the fluid information may further includedisconnecting the vehicle sampling apparatus from the multiphasesampling apparatus; and transporting the fluid sample to a positionremote from the fluid flow line.

Optionally, the step of relaying the fluid information may includediscarding at least a portion of the fluid sample into the fluidflowline by means of a fluid pump included in the vehicle samplingapparatus; transmitting the fluid information to a remote position via acommunication channel between the vehicle sampling apparatus and theremote position, and disconnecting the vehicle sampling apparatus fromthe multiphase sampling apparatus.

Preferably the method is performed subsea. In this aspect, the vehiclesampling apparatus is a subsea remotely operated vehicle (ROV).

In accordance with an aspect of the present disclosure, the multiphasesampling apparatus may include a flow conditioner having a fluidconnector. The sampling connector may be insertable into the fluidflowline by an extension mechanism, or connectable to the fluidconnector of the flow conditioner. The extension mechanism may operatetelescopically.

Further according to an aspect of the present disclosure, the method mayfurther include analyzing the collected fluid sample utilizing a fluidanalysis sensor.

Additionally, the method may include enriching the collected fluidsample. The enrichment of the collected fluid sample may include thesteps of separating the phases of the multiphase fluid sample, storingthe phases of the fluid sample which are of interest and returning theunwanted phases of the fluid sample to the flowline.

The method may also include the step of pressure testing the multiphasesampling apparatus utilizing the fluid pump included in the vehiclesampling apparatus.

The method may also include changing the flow regime of the flowconditioner utilizing the fluid pump of the vehicle sampling apparatus,cleaning the fluid conduits utilizing the fluid pump included in thevehicle sampling apparatus, and cleaning the sampling probe utilizingthe fluid pump included in the vehicle sampling apparatus. In one aspectof the present disclosure, the method may include pumping unwanted fluidback into the flowline utilizing the fluid pump.

According to another aspect of the present disclosure there is provideda sampling probe for use with the system and method as described above.

One of the advantages provided by the current system and method formonitoring and analysis of fluids in a flowline is that it allows theuse of systems and methods for sampling and analysis of fluids to beimplemented in the subsea environment while keeping the sample fluid atline conditions. A further advantage is that the sample probe isremovable from the flowline and may therefore be more protected fromdamage and clogging. Another advantage is the representivity of thesampling process, i.e. the sample phases can be selected and adequatequantities from these sample phases can be captured through anenrichment process. Another advantage is the capability of“no-sample-to-surface” concept wherein a fluid sample may be collected,analyzed on the ROV skid, and discarded back into one of the flowlines.An exemplary system and method of the present disclosure also allows forconvenient cleaning and unblocking of the sample probe and sample fluidconduits.

Even further, the system and method can be adjusted subsea and thus usedfor a very wide range of fluids encountered subsea, from lean gas toheavy oil. The ability for the system to be adjusted is enhanced by theuse of selected sensors which are deployed with the system, and whichallow for the selective sampling of fluids of interest.

The disclosure also provides a method and system for taking oil waterand gas samples in subsea environment under a large range of flowingconditions: high to low gas volume fraction (GVF) and water liquid ratio(WLR), even when there is solid debris present. The disclosure providesa method and system for obtaining in a controlled manner, samples of amultiphase mixture from a line in a subsea environment and separating,via an enrichment process, monophasic samples of water, gas and or oil.

The system and method of the present disclosure include a subseasampling device preferably permanently or semi-permanently attached tothe flowline or wellhead for capturing a multiphase sample from theflowline or wellhead. In one embodiment, subsea sampling device is as acommercially available device called subsea sampler and offered by FramoEngineering. The system further includes a remotely operated vehicle(ROV) sampling skid assembly and a device for docking the ROV to thepermanently installed sampling device and making all electrical, fluidand communication connections as necessary. The ROV sampling skid isequipped with an enrichment system for separating oil, water or gassamples from the multiphase sample, as well as a device for storing theseparated samples in pressurized bottles. Upon docking of the ROV skidto the permanently installed sampling device, the sampling sequence isinitiated to transfer a sample taken from the permanently installedsubsea sampling device to the ROV skid sample enrichment process.Monophasic samples are then collected and stored in the pressurizedbottles on the ROV skid. The ROV skid can then transfer the samples to asurface facility. The system further includes a device for ensuring thatthe samples that are taken are representative (e.g., in terms ofcomposition) of the phases flowing at flowline or well head conditions(e.g., in terms of pressure and temperature). The system allows thetaking of sufficient quantities of monophasic samples to enable furtherfluid analysis, as needed.

It should be understood that the first stage of the process, forexample, connecting to the sample point of interest at the line orwellhead or some other subsea location as may be desired and gettingsample fluids can be performed in several ways. In one embodiment, acommercially available sampling port system offered by FRAMO Engineeringcan be used.

Advantageously, the method and system of the present disclosure allowfor sampling in flows where some solid debris is encountered. The methodand system also allow for separation of the oil/water/gas in largeenough volumes for the full range of WLR and GVF via “phase enrichment.”The enrichment process is made at the same or substantially the sametemperature and pressure as the flowing production line to avoid phasecomposition changes. The enrichment process is continuous and theun-wanted fluids are re-injected into the line. Two possible variationsof the enrichment include performing enrichment inside the samplingbottles themselves in conjunction with a phase identification probe, andperforming enrichment in a sub-unit made of a gas-liquid and anoil-water mini separator. Other variations may be envisioned from thoseskilled in this art without departing from the present disclosure asdescribed in this application.

The samples obtained are taken back to the surface in constant volumebottles, where further enrichment can be made, if necessary.Additionally, oil/water phase present in gas bottle can be transferredto oil or water bottles, by way of complimentary services on surface.The ROV skid assembly may connect and disconnect to ports installed atthe sampling location nearby the wellhead or the flowline.

These together with other aspects, features, and advantages of thepresent disclosure, along with the various features of novelty, whichcharacterize the disclosure, are pointed out with particularity in theclaims annexed to and forming a part of this disclosure. The aboveaspects and advantages are neither exhaustive nor individually orjointly critical to the spirit or practice of the disclosure. Otheraspects, features, and advantages of the present disclosure will becomereadily apparent to those skilled in the art from the followingdescription of exemplary embodiments in combination with theaccompanying drawings. Accordingly, the drawings and description are tobe regarded as illustrative in nature, and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be better understood and aspects other than thoseset forth above will become apparent when consideration is given to thefollowing detailed description thereof. Such description of the presentdisclosure is illustrated by way of example, and not by way oflimitation, to the annexed pictorial illustrations, graphs, drawings,and appendices, in which like reference numerals refer to similarelements, and in which:

FIG. 1 depicts a schematic overview of a sampling system attached to aflowline and attachable to an ROV according to an exemplary embodimentof the present disclosure;

FIG. 2 depicts a schematic overview of an extendable probe samplingsystem attachable to a flow line and attachable to an ROV according toanother exemplary embodiment of the present disclosure;

FIG. 3 depicts a schematic side view of a sampling probe apparatusaccording to an exemplary embodiment of the present disclosure;

FIG. 4 depicts a schematic side view of a sampling probe apparatusaccording to a further exemplary embodiment of the present disclosure;

FIG. 5 depicts a schematic overview of a sampling system having a flowconditioner attachable to an ROV according to an exemplary embodiment ofthe present disclosure;

FIG. 6 depicts a schematic overview of a system and method for samplinggas subsea, according to another exemplary embodiment the presentdisclosure;

FIG. 7 depicts the exemplary system and method of FIG. 6 for waterenrichment subsea, according to the present disclosure; and

FIG. 8 depicts the exemplary system and method of FIG. 6 for oilenrichment subsea, according to the present disclosure.

DETAILED DESCRIPTION

Specific embodiments of the present disclosure will now be described indetail with reference to the accompanying drawings. Further, in thefollowing detailed description of embodiments of the present disclosure,numerous specific details are set forth in order to provide a morethorough understanding of the disclosure. However, it will be apparentto one of ordinary skill in the art that the embodiments disclosedherein may be practiced without these specific details. In otherinstances, well-known features have not been described in detail toavoid unnecessarily complicating the description.

The terminology and phraseology used herein is solely used fordescriptive purposes and should not be construed as limiting in scope.Language such as “including,” “comprising,” “having,” “containing,”“consisting of,” or “involving,” and variations thereof, is intended tobe broad and encompass the subject matter listed thereafter,equivalents, and additional subject matter not recited.

“Isothermal” as used herein refers to a process that takes place withminimal temperature change. Likewise, “isobaric” as used herein refersto a process that takes place with minimal pressure change. For example,“isothermal sampling,” “isobaric sampling,” “at line conditions,” andvariations thereof, as used herein refer to sampling a predominant phaseof a multiphase fluid without substantially changing its composition orstate.

A first embodiment of a system 10 for fluid sampling and analysis in aflowline 12 according to the present disclosure is depicted in FIG. 1.The flowline 12 to which the system 10 according to the presentdisclosure may be applied is preferably for use in the oil or gasindustry.

The present disclosure relates preferably to a system and a method forthe removal, analysis and/or conditioning of fluid, that is, liquid(e.g., oil and water) and gas, from subsea pipelines and seabedproduction equipment containing multiphase fluid flow across a broadrange of fluid types from gas condensates to heavy oils. The presentdisclosure incorporates a multiphase fluid sampling and analysisapparatus and enrichment process for pressure/volume/temperature (PVT)quality samples obtained directly from the flowlines of pipelines in theoil or gas industry. The present disclosure also incorporates a flowconditioner and sampling connection for a subsea pipeline to performflow conditioning and sampling of suitable fluid samples. The samplingconnection can be modified for various methods of deployment and theseembodiments of the apparatus and methods according to the presentdisclosure are described in more detail below. Isothermal heating andsensors are also disclosed to monitor the fluid characteristics for allthe subsea sampling.

In FIG. 1, a sampling apparatus 11 having a subsea sampling probe 14 isdepicted at a position on flowline 12 just after an elbow. This positionis often used for mixing in a typical Vx flowline. The subsea probe 14may be permanently positioned in the flowline 12 after being insertedinto the flowline 12. The subsea probe 14 may be positioned downwardfacing, which is opposite to the typical port for a multiphase samplingdevice, which is upward facing. This is to allow for a remotelyoperating vehicle (ROV) to have access to the subsea probe 14 from aboveflowline 12. A valving system is provided that allows an ROV 16 to forma wet-stab connection onto multiple ports at stab plate connection 18for performing sampling. The ROV sampling system 20 has a pump 22 thatallows the fluids in the hydrocarbon flowline 12 to be drawn into theROV sampling system at a desired rate. The pump 22 is a variable rate,and the flow direction of the pump can be controlled from the ROV 16.

The pump 22 may include a pump cylinder 24, piston 26 and a ball screw28. The outlet (or exhaust) of the sampling system 20 is returned intothe hydrocarbon flowline 12, at line conditions to minimize pressuredrop. This results in very little difference in pressure between theinlet and the outlet of the sampling system 20. If the sample taken fromthe flowline 12 by probe 14 is gas rich with very little liquid, the ROVball screw pump 22, or an additional pumping device, can be used toexhaust the unwanted gas back to the hydrocarbon flowline 12. The liquidcollected may however be kept in the pump cylinder 24 with the use of asuitable water, oil and gas detector. This detector has the ability tomeasure the phase boundary and interface between the different media,the transition between oil and water, oil and gas, gas and water. Thepump's flow direction can be changed to draw in samples and then exhaustundesirable media back into the flowline 12. It will be understood thatpump 22 may operate by other means and is not limited to a ball screwtype.

Once the desired volume of sample has been obtained by probe 14, thesample can then be pumped into a piston sample bottle 30 located on ROV16 for retrieval to the surface. There may be a plurality of samplebottles 30 on ROV 16. Alternatively, however, the sample may be analyzedon the ROV 16. The sample may be subsequently transported to surface bythe ROV 16, or may be exhausted back to the hydrocarbon flowline 12, asdescribed herein. A more detailed discussion of the fluid analysis meansis provided hereinafter.

The pump 22 also can be used to pump debris from the probe 14 if itbecomes plugged during use. The ROV 16 can supply power to heat theprobe 14 assembly to minimize temperature gradients which can lead toheavy wax formation and thus affect the representativity of the sample.This isoheating system may use heat trace type elements or circulate hotwater to provide an isothermal environment for sampling and analysis.This enables the fluid sample to be kept at line conditions.

The fixed probe 14 of the embodiment depicted in FIG. 1 is connected toa manifold via hydrocarbon capable wet-connects (not shown). Alsodepicted in FIG. 1 are pressure and temperature sensors 32 that can beused to monitor line conditions. Heating jackets 34 are also providedaround the probe 14 manifold 36. Typically, these heating jackets wouldalso extend along the full length of the sampling flowlines 38 from asampling point at probe 14 to the sample bottle 30, including the pumpcylinder 24. For example, the fixed probe 14 may be an aerofoil shapedprobe aimed towards selective enriched sampling from a multiphase fluidmixture flowing at high velocities.

There are two main valves in this embodiment of the present disclosure,namely valve 40 and valve 42. While two main valves 40, 42 are depicted,it is understood that any number of valves may be used in accordancewith the present disclosure. Valves 40, 42 allow identified fluids to bedrawn into the pump cylinder 24, and then if any undesirable fluids arepresent, the pump 22 can then push these fluids back into thehydrocarbon flowline 12.

The fluid selection process or enrichment of desired fluids is anadvantageous function for sampling of multiple phase fluids. Theenrichment of the collected fluid sample includes the separation of thephases of the multiphase fluid sample, the storage of the differentphases of the fluid sample, which are of interest, in a sample bottle,and the return of unwanted phases of the fluid sample to the flowline12. Once the desired fluids are captured in the pump cylinder 24, theycan then be pumped through a sampling valve 44 into the sample bottle 30for retrieval at surface, or may be analyzed by the ROV 16 and exhaustedback to the hydrocarbon flowline 12.

The system 10, depicted in FIG. 1, also highlights the use ofhydrocarbon capable wet connects between the flowline 38 and thesampling apparatus 11, depicted as stab plate connector 18. There arefurther electrical connects, namely, a hi-power electrical wet stabconnect 46 for heating jackets and an electrical wet-connect 48 forphase, pressure and temperature sensors 59 and other measurements. Anadvantage of these additional connections being available between thesampling apparatus and the equipment onboard the ROV 16 is that theyprovide powerful electrical connections for the use of the equipmentmaking up the system 10.

Once the fluid sample has been transferred to ROV 16, the fluid can becharacterized, and analyzed subsea in the ROV sampling and analysisskid. The analyzed fluid sample may be returned to surface, or may beexhausted back to the hydrocarbon flowline 12. The latter method may bereferred to herein as the “no-sample-to-surface” concept. Such a conceptcan reduce the turn-around time and health, safety, and environmentalrisks due to live crude at surface.

The ROV sampling and analysis skid can include any suitable knownequipment that makes use of varied forms of any suitable known oilfieldfluid analysis technologies. Such analysis technologies are integratedsubsea into a multi-phase fluid sampling and analysis tool to be usedwith the system and method of the present disclosure. Examples of suchsampling and analysis technologies that may be employed can includewireline technologies, such as a modular dynamics formation tester, amodular dynamics formation tester-pump out, an optical fluid analyzer,low shock sampling, PVT analysis, gamma ray attenuation, or the like.One analysis scheme may be based on a direct measurement of gamma-rayattenuation across the fluid sample in the hydrocarbon flowline 12, orin the ROV 16. As an example for determining this measurement, at leastone detector is placed at a fixed distance (e.g., a few centimeters)from the gamma-ray source, so that the gamma-ray path from the source tothe detector is mainly through the fluid sample.

The permanently positioned sampling apparatus 11 in the flowline 12depicted in FIG. 1 also has the functionality to be ROV replaced formaintenance. During sampling operations, an ROV is deployed and wetmates to this permanently positioned sampling apparatus 11 with probe 14for sampling operations.

An additional embodiment of a system 10 for fluid analysis in aflowline, preferably for use in the oil and gas industry according tothe present disclosure is depicted in FIG. 2. The embodiment depicted inFIG. 2 includes a permanently positioned subsea sampling apparatus 11,but in this embodiment of the present disclosure, subsea probe 14 is notpermanently inserted into the flowline, but is positioned to the side ofthe flowline and may be insertable and extendable into flowline 12 bymeans of a mechanical extension mechanism or means. The result of thisis that probe 14 when not in use is retracted from the flowline and isno longer in contact with the fluid in the flowline. When probe 14 isemployed to take samples, it is then deployed into the flowline 12 forsampling. The deployment of the probe 14 is done by applying hydraulicpressure to a hydraulic ram or a telescopic arm. The hydraulic pressure,measurements and isothermal heating for sampling apparatus 11 areobtained from the ROV 16. The ROV 16 provides hydraulic and electricalpower, as well as communication to the sampling apparatus 11 and probe14, for deployment and sampling. An actuator hydraulic pump 50, locatedon the ROV 16, is connected to a probe actuator assembly 52 for theprobe 14. The pump 50 includes an actuator line 54 for extension and anactuator line 56 for retraction.

The extendable effect of the probe 14 and its ability to move up anddown by the actuator assembly 52 of the probe 14, as illustrated bydouble arrow A, enable the probe 14 to be removed from the flowline andprotects the probe 14 while not in use. FIG. 2 is shown split into twohalves, wherein the probe side is permanent to the subseainfrastructure, and on the other side of the stab plate connector 18,the ROV 16 and ROV sampling system are located. An advantage of thisarrangement is that it reduces the risk of plugging and erosion of thesubsea sampling probe 14.

The probe 14 can be fully stroked to the sampling apparatus 11 deployedposition or the probe 14 can be deployed incrementally to the desiredposition, depending on the flow regime and fluid types, and in order toget the desired sample from the fluid flowline. In addition, whenstroking the probe 14, a phase/fluid detection device (not shown) can beincorporated with the probe 14 to fine-tune the position employed forthe desired fluid sample type. It will also be noted that the extendableor telescopic stab plate for probe 14 of FIG. 2 can have additionalhydraulic wet-stabs for the probe 14 deployment.

System 10 utilizes metal-to-metal dynamic seals and dual barriers.Standard valve pocket geometry and subsea actuator technology also canbe used with system 10, as much as practically possible.

The extendable probe 14 of FIG. 2 also includes an extra probe flushline 58 and two extra flush valves 60. One purpose of these flush valves60 and the flush line 58 is so that after the ROV 16 connects to thestab plate connector 18, the hydraulic lines of system 10 can bepressure tested before opening the main barrier or seal to the flowline.There are many ways in which this can be done, but it is advantageous tonote that the flush line 58 can be pressure tested subsea by the ROV 16and the main barrier can be opened after a successful test. The samplingcircuit of system 10 may be flushed by using the pump 22 prior or afterthe probe 14 deployment to make sure that sampling lines and flush linesare clear of debris and unwanted fluids. Fluid identification sensorscan be used immediately, as the ROV 16 connects to the stab plateconnector 18, to indicate fluid types and warn of any potential leakage.

A further embodiment of the system and method for fluid sampling andanalysis according to the present disclosure includes a sampling probe14, which is designed to be positioned at any subsea point that is ROVaccessible. This sampling probe 14 extends into the flowline 12 anddepending on the mechanics of the extension means may movetelescopically in the flowline 12 or extend on a ram. This does not relyon the Vx flowline 12 to enable the sampling probe to be attached onlyat a position upstream of an elbow portion of the flowline 12 so as tofocus fluids for the probe to sample. The probe 14 according to thisembodiment of the present disclosure is independent of the geometry ofthe fluid flowline 12 and this is accomplished by the probe inlet ports,which are capable of being extended across the internal diameter of thefluid flowline 12. The probe 14 can be positioned to allow capture ofthe desired samples and to accomplish this accurately, an optical phasedetector may be located on the probe 14. In this way, it is alsopossible for the probe 14 position to be moved across the bore of thesubsea production flowline 12 for fluid selection prior to sampling.

Examples of sampling probe apparatus, according the present disclosure,are depicted in FIGS. 3 and 4. In FIG. 3, the subsea sampling probe 14is shown to include a sample chamber 62, a floating piston 64, inletports 66, a closing mandrel 68 and seating piston 70. The flowing boreof interest is indicated by line 72 in FIG. 3.

A further embodiment of the system and method for fluid sampling andanalysis according to the present disclosure includes the use of alubricator type probe deployment. In this embodiment of the presentdisclosure, the sampling probe 14 is completely removed from the subseamanifold in which it is housed during sampling and it is then fitted tothe ROV 16. This configuration employs a lubricator type system topressure seal and deploy the probe 14.

An additional embodiment of the present disclosure includes a samplingapparatus having a flow conditioner 502, as depicted in FIG. 5, such asthe flow conditioner disclosed in co-pending U.K. Patent ApplicationNos. 2406386A and 2447908A, the disclosures of which are herebyincorporated by reference. The flow conditioner 502 can be used tocondition flow 504 via inlet 506 for best sampling. The flow conditioner502 may be adapted to fit any size flange, or sampling connection andflow regime, according to well specifications, and includes an outlet520. The connections 510 with the flow conditioner 502 are operablethrough the ROV 16, and are often referred to as hot-stab connections.

Further advantages of utilizing the flow conditioner 502 with thepresently disclosed system include the ability to separate a fluidsample into suitable liquid samples 512 from output 514 or gas samples516 from output 518. As an example, separation means may include:cyclonic separation, inline cyclonic separation, gravity separation,mechanical separation, and/or secondary separation. The flow conditioner502 having separation capabilities may be permanently or temporarilyconnected to the flowline 12. Alternatively, the flow conditioner 502may be incorporated as part of the ROV 16 skid (not shown), therebyallowing customized flow conditioning of fluid without the need forpermanent placement. Such a flow conditioner of an ROV may be adaptedfor connection with a flow conditioner of the multiphase samplingapparatus. The method for collecting a fluid sample using the flowconditioner 502 is similar to the method described with reference toFIG. 1.

Additional embodiments of the present disclosure may further include afull bore pipeline bypass in the ROV 16, thereby improving theintervention of flow conditioners, sampling connections and samplingprobes. Full bore pipeline bypass provides the advantage of morecontrolled isoheating and isobaric sample collection. Furthermore, fullbore pipeline bypass provides a method for obtaining a flow sample usingcomplex probes and sensors which are impractical for permanentinstallation on a subsea fluid flowline system. A full bore bypass inthe ROV 16 may be integrated with a flow conditioner, also included inthe ROV 16.

The pressure testing and flushing of the wet stabs are an additionalaspect of an exemplary embodiment of the current disclosure. Once allvalves have been tested, opened and flushed, the sampling collectionoperation can commence. Once complete, the sample system 10 again can beflushed to clean up all the lines for storage. Again, the fluid sensorsin the internal diameter of the flowline can be used to indicate whenthe hydrocarbons have been removed from the flowlines for saferetraction of the sampling probe. Once this has been done, the mainhydrocarbon barriers can be closed, and can then be pressure tested.Once the operation is complete, the ROV 16 can disengage and return tosurface with samples.

The flushing and pressure testing of sampling valves, probes and linescan be done by the ball-screw pump 26 or the actuator hydraulic pump 50.The flushing fluid can come from the sea or from the ROV 16. Typically,during flushing and sample purging of the sample lines, and whichprovide first hydrocarbons after the flushing, the waste fluid can beexhausted into the production pipeline. The sensors in the system alsocan be used to check the purge fluid content.

There is provided a variation of the system 10, wherein an extendableprobe overlaps with the system using the lubricator option. With thelubricator option, the flowlines full bore is opened to support anintervention of any suitable variety, such as deployment of wirelinetool or some other large device for taking samples from the flowline.Advantageously, this option allows for the capture of the sample at linepressure and temperature. With the use of two barriers valves, thesystem may also use BOP (blow out preventer) technology for probedeployment.

Line pressure is relatively straight forward to maintain, as thepressure is a function of flow rate, which can be easily controlled bythe ball screw pump 26. However, temperature is more complicated and thetemperature gradients can be quite severe. For the samples to berepresentative, they are typically caught at line conditions. If thetemperature varies from the sampling point to the sample, the fluid canchange in equilibrium during its travel from the sampling point to thesample and thus produce unrepresentative measurements. A techniquepresented for overcoming such a problem is to capture the sample in thesample probe. An advantage to this method is that there would be lessneed for heating of the system during sampling.

With limited space for the probe and the probe sample bottle design, asecond probe can be used that may be 180° opposite to allow addedfunctionality to take place. This has been depicted in FIG. 2. Forexample, a probe 14 from the opposite flange can be used to seal thesample into the probe sample bottle or to pump out any unwanted fluidsfrom the probe or to transfer as heating is applied to the system andkeep the samples at flowline conditions.

In FIG. 4, an inlet port 66 is depicted on the probe 14 having anenrichment cylinder 74, which may be at flowline pressure andtemperature conditions. A transfer probe 76 is further depicted oppositethe probe 14 and this transfer probe 76 closes the inlet port 66 of theenrichment cylinder 74, and thereby allows the fluid sample to betransferred at flowline pressure and temperature.

The pump that can be used with the system and method of the presentdisclosure may also provide interactive control of the sampling rate andthe pressure drop. The pump may further be used to unblock the probe bypumping fluids through it or it may be used to remove debris from theprobe. Even further, the pump may be used to pressure test lines priorto and after sampling.

Subsea analysis can be done in the ROV 16, while attached to the subseaproduction pipe or while en route to another sampling point. Fluidsamples also may be retrieved back to surface for further analysis.

FIG. 6 illustrates another exemplary system and method for samplingfluids subsea. FIG. 6 is used for illustrating the sampling gas from atop port and shows the various components of the system according to oneembodiment of the disclosure. Referring to FIG. 6, the method of presentdisclosure includes the following steps:

Step 1: A remotely operated vehicle (ROV) sampling skid assembly 601connects remotely to a subsea, permanently installed subsea sampler 602.

Step 2: A flushing module 603 pressurizes the system and makes thepre-job pressure test.

Step 3: A volumetric piston pump 604 and a set of valves creates a flowstream between the two ports of the subsea sampler ports 605 and 606 viavarious internal pipes prefilled with a buffer fluid. This step allowsremoval the buffer fluid and allows adjustment of the piston pump regimeto optimize the phase to be sampled. During this step, the phases areidentified using phase detector probes (e.g., optical probes).

Step 4: The valves are set to direct a gas sample to the gas samplingbottle 607, while the buffer fluid from a back piston of the samplingbottle 607 is released to an exit port. The bottle 607 filling isstopped when the pressure in the bottle 607 starts to increase.

Steps 5 and 6: Using bottles 608 and 609, these steps are similar tostep 4, except that the valves are set to move the liquid sample fromthe predominantly liquid port 606.

A further step of water enrichment can be performed by deviating thebottle 609′ by few degrees up or down, as shown in FIG. 7, depending onwhether or not water or oil is to be accumulated. This process makes useof the specific configuration of the sampling bottles 607, 608, 609,which have two connection ports on their end caps. Both ports arelocated on a vertical diameter, forming a low port 611 and a top port610. The port 610 of the bottle 609′ is open to let the flow through,wherein the sample stream continues to flow within the bottle 609′ andsegregates by gravity. For concentrating water, as shown in FIG. 7, thebottle 609′ is deviated upward by few degrees (e.g., about 10 deg),wherein the sample stream enters the bottle 609′ via the low port 611and exits via the top port 610. Within the bottle 609′, the wateraccumulates via gravity, wherein the sampling is stopped when the phasedetectors (e.g., optical probe 612, 613) start to detect water comingout from the bottle 609′. Advantageously, such a mechanism allows forcapturing of water, even for very small water liquid ratio (WLR) in theline, wherein in this case the sampling time will be longer than for alarger WLR. A similar process, but with the bottle 609′ deviateddownward can be used to concentrate oil from a liquid sample stream.

Step 7: The bottles are securely closed by a bulkhead manifold and thesubsea sampler 602 valves closed.

Step 8: The flushing module 603 pressurizes the system and makes thepost-job pressure test. The system then disconnects and the ROV skid 601returns to the surface.

One advantage of this system is its ability to selectively sample fromthe two ports of the line to be able to collect and enrich the phasesamples at line conditions pressure and temperature (P, T).

The enrichment process of the system described in FIGS. 6 and 7 may besomewhat limited for the case where oil enrichment is employed and theliquid sample stream contains a small amount of gas. In theseconditions, gas may accumulate in the oil bottle during the enrichmentprocess, thus inhibiting the enrichment of the oil sample. In somecases, the sample may end up full of gas.

Another embodiment of the present disclosure is shown in FIG. 8. Thesystem and method of FIG. 8 is suitable for enriching an oil sample froma liquid sample stream even when the sample contains some gas. Referringto FIG. 8, the phase separation during the sampling steps 4, 5 and 6 ismade using two small separators, one separator 614 for gas/liquid andanother 615 for oil/water. The sample stream generated by the pistonpump is first sent to the gas liquid separator 614, where liquidsegregates from gas via gravity. The level in the separator iscontrolled by on/off valves and three phase detectors (e.g., opticalprobes, 616, 617, 618). The gas is directed to the gas bottle ordiverted to an exit if the bottle is full.

The liquid stream is directed to the liquid separator 614, where the oiland water levels are also controlled by two phase detectors (e.g.,optical probes, 619, 620) and on/off valves. Both phase streams are thendirected to the adequate bottles until full or diverted to an exit. Thisembodiment offers, among other things, the following additionaladvantages:

It is less dependent upon the quality of the primary sample stream andthus, can work as long as the three phases are available in the samplestream. Advantageously, this provides more flexibility on the samplingports installed on the line. Also, the sampling bottles do not requirebeing at well temperature, like in the previous embodiment, and thecompactness of the system is improved and therefore easier to operate.

An additional component of the disclosure is the inclusion of a thermalmanagement system (e.g., passive or active), and which facilitates thesample process to take place isothermically with respect to flowingproduct line conditions. The heating systems (e.g., shown with “X” and“Y” in FIGS. 6-8) may be partitioned to allow separate heating zones tobe controlled. Advantageously, this allows the bottle section to bethermally controlled on an independent or interlocked basis with theheating zone surrounding the sample process pump and valves. Zonalseparation also allows for differing heating media to be applied, suchas oil or water jacket heating systems, electric blankets, and the like.

The heating zones can be set preferably to line condition temperaturesprior to and during the sample process. The temperature level to be setcan be defined either by manual input, or in an automated manner, forexample, by way of link to a temperature sensor (e.g., either located onthe skid 601 or located within the permanently installed samplesystem/line conditioner). The heating systems are linked to the samplingskid 601 control system, and monitored at the surface.

Although the present disclosure has been described with reference toexemplary embodiments and implementations thereof, the presentdisclosure is not to be limited by or to such exemplary embodimentsand/or implementations. Rather, the systems and methods of the presentdisclosure are susceptible to various modifications, variations and/orenhancements without departing from the spirit or scope of the presentdisclosure. Accordingly, the present disclosure expressly encompassesall such modifications, variations and enhancements within its scope.

1. A system for collecting fluid samples from a fluid flowline,comprising: a multiphase sampling apparatus attachable to the fluidflowline which is able to collect a multiphase fluid sample from thefluid flowline; and a vehicle sampling apparatus locatable proximate thefluid flowline, connectable to the multiphase sampling apparatus, andoperable to transport the collected fluid sample remotely from the fluidflowline, said vehicle sampling apparatus including a fluid samplecollector, and a fluid pump that transfers the collected fluid samplefrom the multiphase sampling apparatus to the fluid sample collector. 2.The system of claim 1, wherein the vehicle sampling apparatus furtherincludes at least one fluid analysis sensor capable of analyzing thecollected fluid sample.
 3. The system of claim 2, wherein the fluidanalysis sensor is capable of providing a sample analysis at a subsealocation.
 4. The system of claim 1, wherein the multiphase samplingapparatus further includes a sampling probe which is insertable into thefluid flow and which is able to collect a multiphase fluid sample fromthe fluid flowline.
 5. The system of claim 4, wherein the sampling probeis insertable into the fluid flowline by an extension mechanism when asample is to be collected.
 6. The system of claim 5, wherein thesampling probe is retractable from the fluid flow of the flowline bymeans of the extension mechanism when the sampling probe is not to beused for taking a sample.
 7. The system of claim 4, wherein the samplingprobe includes at least one fluid analysis sensor.
 8. The system ofclaim 1, wherein the vehicle sampling apparatus further includes a fluidconnector which allows the transfer of the fluid sample collected by themultiphase sampling apparatus to the vehicle sampling apparatus.
 9. Thesystem of claim 1, which is locatable subsea.
 10. The system of claim 1,wherein the vehicle sampling apparatus is a subsea remotely operatedvehicle.
 11. The system of claim 1, further comprising a fluidenrichment mechanism that enriches a selected phase of the sample fluid.12. The system of claim 11, wherein the fluid enrichment mechanism forthe collected fluid sample further includes a separator that separatesthe phases of the multiphase fluid sample.
 13. The system of claim 12,wherein the fluid enrichment mechanism stores the phases of the fluidsample which are of interest and returns unwanted phases of the fluidsample to the flowline.
 14. The system of claim 1, wherein themultiphase sampling apparatus is permanently attached to the fluidflowline.
 15. The system of claim 1, wherein the multiphase samplingapparatus is locatable proximate the fluid flowline.
 16. The system ofclaim 1, wherein the multiphase sampling apparatus is locatable on thevehicle sampling apparatus.
 17. The system of claim 1, wherein the fluidpump of the vehicle sampling apparatus functions further to clean thefluid flowline.
 18. The system of claim 4, wherein the fluid pumpfurther functions to clean the sampling probe.
 19. The system of claim1, wherein the vehicle sampling apparatus further includes a flowconditioner.
 20. A system for collecting fluid samples from a fluidflowline, comprising: a multiphase sampling apparatus attachable to asubsea fluid flowline so as to be in communication with a multiphasefluid flow in the flowline, and including a flow conditioner andsampling connection that selectively communicates with the fluid flowfor selective collection of a fluid sample; and a vehicle samplingapparatus connectable to the multiphase sampling apparatus and includinga fluid connector capable of transferring the fluid sample between themultiphase sampling apparatus and the vehicle sampling apparatus; afluid sample collector adapted to contain the fluid sample for aselected period of time; a fluid pump in communication with the fluidconnector; and at least one fluid analysis sensor operable from alocation remote from the multiphase sampling apparatus.
 21. A method ofcollecting and analyzing fluid samples from a fluid flowline, comprisingthe steps of: attaching a multiphase sampling apparatus to a fluidflowline; attaching a vehicle sampling apparatus to the multiphasesampling apparatus, and transferring the fluid sample from themultiphase sampling apparatus to a fluid sample collector of the vehiclesampling apparatus by means of a fluid pump included in the vehiclesampling apparatus.
 22. The method of claim 21, further including thesteps of: obtaining fluid information relating to the fluid sample fromat least one fluid sensor locatable on the vehicle sampling apparatus;and relaying the fluid information to a remote position.
 23. The methodof claim 21, further including the steps of: collecting the multiphasefluid sample by inserting a sampling probe of the multiphase samplingapparatus into the fluid flowline; and connecting fluid conduits betweenthe multiphase sampling apparatus and the vehicle sampling apparatusprior to transferring the collected fluid sample from the multiphasesampling apparatus to the sample collector of the vehicle samplingapparatus.
 24. The method of claim 22, wherein the step of relaying thefluid information further comprises: disconnecting the vehicle samplingapparatus from the multiphase sampling apparatus; and transporting thefluid sample to a position remote from the fluid flow line.
 25. Themethod of claim 22, wherein the step of relaying the fluid informationfurther comprises: discarding at least a portion of the fluid sampleinto the fluid flowline by means of the fluid pump included in thevehicle sampling apparatus; transmitting the fluid information to aremote position via a communication channel between the vehicle samplingapparatus and the remote position; and disconnecting the vehiclesampling apparatus from the multiphase sampling apparatus.
 26. Themethod of claim 21, which is performed subsea.
 27. The method of claim26, wherein the vehicle is a subsea remotely operated vehicle.
 28. Themethod of claim 23, wherein the sampling probe is insertable into thefluid flowline by an extension mechanism.
 29. The method of claim 21,which further comprises analyzing the collected fluid sample by means ofa fluid analyzer.
 30. The method of claim 21, which further comprisesenriching a phase of the collected fluid sample.
 31. The method of claim30, wherein the enrichment of the collected fluid sample may furtherinclude separating the phases of the fluid sample, storing the phases ofthe fluid sample which are of interest and returning the unwanted phasesof the fluid sample to the flowline.
 32. The method of claim 21, furthercomprising the step of pressure testing the multiphase samplingapparatus and the vehicle sampling apparatus.
 33. The method of claim21, which further includes the step of pumping unwanted fluid back intothe flowline by means of the fluid pump.
 34. The method of claim 23,which further includes the step of cleaning the fluid conduits in thesystem by means of the fluid pump.
 35. The method of claim 23, whichincludes the step of cleaning the sampling probe by means of the fluidpump.
 36. A system for collecting fluid samples from a subsea structure,the system comprising: a subsea sampler device permanently orsemi-permanently attached to the subsea structure and equipped with adevice for capturing a multiphase sample from the subsea structure; anda remotely operated vehicle (ROV) sampling skid assembly including anenrichment system for separating water, gas and/or oil intosubstantially monophasic samples from the multiphase sample, and adevice for storing the separated samples on the ROV skid.
 37. The systemof claim 36, wherein the subsea structure includes one of a fluidflowline, and a wellhead.
 38. The system of claim 36, wherein the ROVskid transfers the samples to a surface facility.
 39. The system ofclaim 36, further comprising a device for ensuring that the samples thatare taken are representative in terms of composition and conditions,including pressure and temperature, of the phases flowing at the subseastructure.
 40. A method for collecting fluid samples from a subseastructure, the method comprising: permanently or semi-permanentlyattaching a subsea sampler device to a subsea structure; capturing amultiphase sample from the subsea structure with the subsea samplerdevice; separating water, gas and/or oil into substantially monophasicsamples from the multiphase sample by an enrichment system of a remotelyoperated vehicle (ROV) sampling skid assembly; and storing the separatedsamples on the ROV skid.
 41. The method of claim 40, wherein the subseastructure includes one of a fluid flowline, and a wellhead.
 42. Themethod of claim 40, further comprising the ROV skid transferring thesamples to a surface facility.